FFmpeg is a free software project that produces libraries and programs for handling multimedia data.
Download link: https://ffmpeg.org/download.html
FormatFactory is an ad-supported freeware multimedia converter that can convert video, audio, and picture files. It is also capable of ripping DVDs and CDs to other file formats, as well as creating .iso images. It can also join multiple video files together into one.
How to extract audio from video using FFmpeg:
If you just want to copy the audio stream without re-encoding just do:
ffmpeg -i input-video.avi -vn -acodec copy output-audio.aac
-vn is no video.
-acodec copy says use the same audio stream that's already in there.
Read the output to see what codec it is, to set the right filename extension.